Adjustable reactance



Nov. 1, 1955 w. v. TYMINSKI ADJUSTABLE REACTANCEI Filed Jan. 5, 1953 w N NI m mT V. m m W 9 9 I F United States Patent ADJUSTABLE REACTAN CE Walter V. Tyminski, Nntley, N. J., assignor to Allen B.

Du Mont Laboratories, Inc., Clifton, N. J., a corporation of New Jersey Application January 5, 1953, Serial No. 329,531

Claims. (Cl. 336-20) This invention relates to electrical reactance coils and particularly to such coils wherein the reactance thereof may be adjusted.

An electrical coil must be rigidly constructed in order that it be stable and negligibly affected by vibrations. In the past, adjustable inductance coils have been constructed having a rigid coil with a movable adjustment slug positioned in the coil. Also, adjustable coils have been constructed having spaced turns, the inductance thereof being adjusted by expanding the spacing between the turns of the coil. Such coils, however, do not provide desired reactive characteristics for certain requirements.

An object of the invention is to provide an adjustable reactance coil which is substantially rigid and self-supporting, and which does not require a tuning slug.

Another object is to provide an adjustable reactance coil which is stable and economical to manufacture.

Other objects will be apparent.

In the drawing,

Figure 1 is a side elevational view of a coil constructed in accordance with a preferred embodiment of the invention;

Figure 2 is an end view of Figure 1;

Figures 3 and 4 illustrate various ways in which the inductance of the coil may be decreased;

Figure 5 shows a modification of the invention wherein a portion of the coil is supported by an insulative post;

Figures 6 and 7 show equivalent electrical circuits of inductive coils;

Figure 8 is a graphic illustration of electrical or reactive characteristics of inductive coils; and

Figure 9 is a graphic illustration of the electrical or reactive characteristics of a coil constructed in accordance with the invention.

The coil, preferably of the solenoid type as shown, is constructed to have a rigid portion 11 comprising one or more turns of electrically conductive wire. This portion 11 is made rigid by impregnation with wax, plastic, or the like, or it may be supported by means of an insulative tubing or rod around which the turns are wound as shown in Figure 5. The remaining turns of the coil comprise a flexible adjustment portion 13 of a turn or fraction of a turn, and a further rigid portion 12 of one or more turns. The flexible portion 13 may be extended or compressed as desired thus forming the required adjustment. The spacing 13 may be, in effect, an elongated turn of the coil. The portions preferably comprise a continuous length of Wire.

The ends of the coil extend to provide connecting portions 14 and 15 to which electrical circuit connections may be made. The coil may be self-supporting by means of the connecting portions 14 and 15 being securely afixed to other objects, or as mentioned above the coil may be supported in full or in part by an insulative post 16 on which the rigid portion 11 is wound, as shown in Figure 5. If desired, the post 16 may extend through the adjustment portion 12, this portion having a larger diameter than the post so as to be slidable thereon.

The coil is initially constructed with a spacing 13 to provide an optimum or normal inductance value for the coil. After the coil has been connected into the electrical circuit for use, the reactive value thereof may be trimmed or adjusted to be made higher or lower merely by compressing or expanding the spacing 13 between the portions 11 and 12 of the coil. The end portions 14, 15 can be bent or flexed to take up the slack.

To adjust to a lower value of inductance, the portions 11 and 12 of the coil are spread apart, thereby increasing the spacing 13.

Instead of increasing the spacing 13 in an axial direction to decrease the inductance of the coil, as has been described, thetwo portions 11 and 12 of the coil may be offset, or bent at an angle, as shown in Figure 3. To decrease inductance still further, the adjustment portion 12 of the coil may be bent with respect to the rigid portion 11, as shown in Figure 4, where the electrical fields of the portions 11 and 12 are in opposition, thereby decreasing the total inductance.

A coil constructed in accordance with the preferred embodiment of the invention has been found to permit a variation in inductance of at least or 10% of its preset optimum value. If desired, the turns of the adjustable portion 13 and the further fixed portion 12 may be impregnated after adjustment with a material so as to make them rigid.

Coils in accordance with the invention have been found to provide stable inductance values once the desired adjustment has been made by varying the spacing 13.

A physical inductance has a shunt capacity from turn to turn as shown in Figure 6 and the total coil can be approximated by a lumped inductance in parallel with a single capacitance as shown in Figure 7. The reactance of this combination is shown in Figure 8, wherein wL represents the reactance Without the shunt capacitance and Xe is the effective reactance including the eflfect of the shunt capacity. Thus it can be seen that the apparent physical inductance is in reality a capacitance above frequency wo.

In accordance with this invention the physical inductance is separated into two physical parts both with self resonant frequencies above that obtainable with a single continuous coil and the reactance is as shown in Figure 9.

Not only does this arrangement make possible the physical realizability of a coil having self-resonance above the frequency L04, the point of self resonance of a single continuous inductance, but other effects become apparent. The coil is series resonant at frequency ms and presents a zero reactance at this frequency while presenting a reactance at all other frequencies. Further, there is an additional range of inductive reactance above the self resonance point an of the longer coil. Finally, there are two ranges of capacitive reactance above the point all.

Preferably, the adjustment portion 12 has fewer turns than does the rigid portion 11. Thus, the major portion of the coil is rigidly supported. In practice, satisfactory coils have been made with the rigid portion comprising of the total turns, and with the adjustment portion comprising /3 of the total turns.

While preferred embodiments of the invention have been shown and described, various modifications thereof will be apparent to those skilled in the art. The scope of the invention is defined in the following claims.

What is claimed is:

1. An adjustable reactance coil comprising a solenoidal coil of continuous Wire of substantially the same diameter having a plurality of turns, some of said turns forming a rigidly supported group, others of said turns formti ing another rigidly supp rted group, and an adjustable spacing turn between and electrically and rigidly mechanically connecting said groups of runs one of said groups of turns being movable with respect to the other of said group of turns about said adjustable spat 0 turn.

2. An adjustable reactance coil comprising a so noidal coil of continuous Wire of substantially the same diameter having tWo groups of tur s separated and electrically and rigidly mechanically connected able expanded turn, one of said groups being ri iorted, and the other said group being movable ct to said rigidly supported group about said a 3. An adjustable reactance coil comprising a solenoidal coil of continuous wire of substantially the same diameter having two groups of turns separated a panded turn, and an insulative support rner. said groups of turns being positioned on ported by said support member the other of a: of turns being movable With respect to said group about said adjustable turn.

4. An electrical inductance member comprising a plurality of turns of electrical conductive material having capacitance therebetween, at least one of said turns being adjustably elongated to provide a plurality of rigid groups of turns electrically and rigidly mechanically connected together, the inductance and capacitance of each of said groups of turns providing higher frequencies of self-resonance than that in a corresponding group of turns in a coil which is not elongated one of said groups being movable with respect to the other of said groups about said adjustable turn.

5. The inductance member in accordance with claim 1 in which said groups of turns comprise differing numbers or" turns, sat groups of turns having a plurality of differing self-resonance frequencies to provide pluralities of frequency bands having differing reactive impedances.

"eiences Cited in the file of this patent UNlTED STATES PATENTS 

